What you see depends in large part on how far you travel from Iquitos . The riverbanks that were mostly wilderness in the 1960s are now wall-to-wall farms and cow pastures. Most of the jungle within 80 kilometers of Iquitos is secondary forest, but dolphins, monkeys, and birds can still be seen.
The jungle gets more interesting the farther away you travel. Reserva Nacional Pacaya Samiria  (12 hours upstream) and the Reserva Comunal Tamshiyacu Tahuayo (4–6 hours) have wildlife and pristine jungle comparable to Parque Nacional Manu  in Peru’s southern Amazon.
One advantage that that this jungle region has over Peru’s southern Amazon is that even during the rainy season, it typically only rains in the afternoon, so jungle lodges  can be visited year-round. It’s also the only place in Peru where pink river dolphins live.
There is a high-water season, however, between January and June, when the Amazon rises 15 meters and floods much of the surrounding forest. Guides say there are more birds during these months, though mammals are easiest to see during the low-water months of July–December when they hang out on the muddy riverbanks. The number of monkeys seems to hold steady year-round.
The land that does not become flooded is called terra firma or restinga and has different animals. Typical birds in a flooded forest include flycatchers, tanagers, woodcreepers, kingfishers, finches, woodpeckers, parrots, macaws, and all species of cotingas.
Because there is more food in a nonflooded forest, there is a greater variety of mammals and reptiles and different birds, including antbirds, manakins, curassows, guans, foliage cleaners, and all species of woodcreepers and woodpeckers. To see the greatest range of wildlife and birds, choose lodges that have access to both flooded forest and terra firma.
Competition is intense among the jungle outfits in Iquitos, and discounts are sometimes handed out to those who make their reservation in town, as opposed to over the Internet.
If you come into town without a reservation, use the agencies, lodges, and guides recommended here and, when in doubt, consult the Iperú or Dircetur office listed.